The invention relates to an arrangement for forming a helical tube having a given length.
An arrangement is known from EP 0384625 in which in a first stamping station a flange is made on a metal strip. This metal strip is then bent into a spiral-shaped form inside a forming tool and the edges of the sides which make contact with each other are flanged together. A cutting arrangement subsequently cuts the helical tube off into predetermined lengths.
Such helical tubes are made of perforated metal sheet and are used, for instance, in filter technology to provide an inner or outer support pipe for a cylindrical filter element, for example a zig-zag shaped folded filter paper. Here it is important to note that the length of the helical tube has a very low permissible variation so that matching with the other elements and the arrangement of end plates can occur properly. It has been shown that, with the currently known arrangements, the length and the evenness of the helical tube vary greatly, on the one hand because during preparation its dimension can only be determined with difficulty and on the other hand because certain impurities from the added processing liquid caused inaccuracy.